System for automated boot from disk image

ABSTRACT

A system allowing a target machine to be booted up from a disk image stored in memory. Instead of reading the boot-up information from a disk drive or other physical device the data is read from memory. No modification is necessary to native operating system, input/output subsystem, bootstrap code, etc., since the invention modifies characteristics, such as vectors used by the operating system, to make the disk image in memory appear to be the same as a standard external device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to the following U.S. patent applicationswhich are hereby incorporated by reference as if set forth in full inthis document:

Ser. No. 09/663,252 entitled “USER INTERFACE FOR DYNAMIC COMPUTINGENVIRONMENT USING ALLOCABLE RESOURCES” filed on Sep. 15, 2000;

Ser. No. 10/241,808 entitled “SYSTEM FOR MANAGING BOOT-UP OF TARGETCOMPUTERS” filed on Sep. 10, 2002; and

Ser. No. 10/241.749 entitled “USE OF OFF-MOTHERBOARD RESOURCES IN ACOMPUTER SYSTEM” filed on Sep. 10, 2002.

BACKGROUND OF THE INVENTION

This invention relates in general to digital data processing and morespecifically, to a system for managing start-up, or boot-up of computersystems.

When a computer system is first powered up many functions must takeplace to put the computer into an operational stage. These functions arecommonly referred to as “boot-up,” “booting,” “bootstrapping,” “bootingup,” etc.

Typically, the booting procedure is well defined for any given machine.However, procedures can vary from computer to computer especially wherethe computers have different resources and peripherals, are configureddifferently, have been made by different manufacturers, are intended toexecute different software, etc.

In some computer applications, it is desirable to coordinate,interconnect and configure multiple computer systems so that morecomputing power, or resources are available. The prior art provides someways to control the boot-up of a target machine, such as a personalcomputer (PC). For example, one common prior art method is to boot froman executable image on a floppy disk.

Typically, if a floppy disk is detected in a PC's floppy drive duringboot-up, the PC loads the executable image from the floppy drive andtransfers control to the executable image. By providing boot-up from afloppy, users can easily direct specific booting of their machines. Thisapproach works well for situations where a user wants to, e.g., boot toa specific operating system, allow an application to take control of thePC at boot-up, etc. However, this approach is not desirable whenautomated booting of many different machines is desired since insertinga floppy disk into a PC is a manual operation. When there are dozens,hundreds, or thousands of target machines to be managed, the approach ofbooting from a physical floppy is prohibitive.

BRIEF SUMMARY OF THE INVENTION

The present invention allows a target machine to be booted up from adisk image stored in memory. Instead of reading the boot-up informationfrom a disk drive or other physical device the data is read from memory.No modification is necessary to native operating system, input/outputsubsystem, bootstrap code, etc., since the invention modifiescharacteristics, such as vectors used by the operating system, to makethe disk image in memory appear to be the same as a standard externaldevice.

Multiple floppy images are supported as separate floppy drives (e.g., A:and B:). User-defined arguments can also be passed from a server to abooted machine. This allows the server to have additional control overhow programs on the floppy images execute. OpForce supports both an A:and a B:.

In one embodiment the invention provides a method for using a computersystem to execute information stored on a physical medium, the methodcomprising copying information in the physical medium to an electronicfile; storing the electronic file in random access memory in thecomputer system; changing one or more characteristics in the computersystem so that a process executing in the computer system is providedwith data from the stored electronic file when an access to a physicaldevice is attempted; and using the computer system for executing atleast a portion of the information in the random access memory.

In another embodiment the invention provides an apparatus for managingboot-up of a target computer, the apparatus comprising a servercomputer; memory within the server computer for storing an image of aboot disk; and code stored within the server computer for directing thetarget computer to access a part of target computer memory instead of aphysical peripheral.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an application of the system of the present invention;

FIG. 2 illustrates steps in a managed boot-up procedure; and

FIG. 3 depicts a memory map illustrating details of booting using a diskimage.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an application of the system of the present invention.

In FIG. 1, server 102 is a computer system for managing target machinesin a configurable network. The configurable network is represented byresources 104. Any type of processing equipment or devices can beconsidered resources including processing units, memory, communicationbandwidth, storage, functionality, etc. Such resources can be providedby software, hardware or a combination of both.

Server 102 detects when target machines such as 106, 108 and 110 areinitially powered up. A preferred embodiment of the invention requires ahuman administrator to manually power up one or more target machines.Other embodiments can automate the power-up process. Server 102 thenacts to control the boot up of one or more of the target machines, asdesired. During boot-up, characteristics and resources that are local toa specific target machine (e.g., disk drive, random-access memory (RAM),processor type, peripherals, communication ability such as networkcards, etc.) are determined or “discovered” and reported back to theserver. After controlled boot-up and discovery, server 102 can alsoactivate, allocate, or configure, resources, including resources 104, towork with a target machine. Server 102 can manage operations includingloading software on the target machines, directing interconnectivity oftarget machines on a network, etc.

A preferred embodiment of the invention is adapted for use with dynamiccomputing environments (DCEs) such as the DCE described in co-pendingU.S. patent application Ser. No. 09/663,252 entitled “USER INTERFACE FORDYNAMIC COMPUTING ENVIRONMENT USING ALLOCABLE RESOURCES” filed on Aug.15, 2000.

Target machines can be any type of computer system or other processingdevice. For example, personal computer systems, servers, workstations,mainframes, etc., can be target machines. Such machines can be basedaround different manufacturers' designs such as Intel, Advanced MicroDevices (AMD), SUN Microsystems, etc. Different models, versions andconfigurations of machines are typically available from eachmanufacturer. For example, some machines may vary in the processor type,attached peripherals, internal memory capacity, communication ability,etc. Target machines can also be devices that are not based on a generalpurpose microprocessor design. For example, target devices can be basedon parallel processing, distributed processing, asynchronous or otherdesigns. Target machines can be standalone peripherals, network devices,etc. Target machines can use customized circuitry, application-specificintegrated circuits (ASICs), field-programmable gate arrays (FPGAs),discrete, dedicated or custom circuitry, etc. In general, any type ofdevice, including digital, analog, mechanical, biotechnology, optical,etc. can be a target machine.

In the preferred embodiment, the target machines are interconnectedbased on a specific configuration. The interconnection mechanism can beby hardwire, fiberoptic, wireless or other type of communication link. Adigital network such as, e.g., Ethernet, IEEE 1394, universal serial bus(USB), 802.11b, etc. can be used. In a preferred embodiment, the linkingof communication channels between target machines, the server, externaldevices and networks (such as the Internet), etc., is controlled andmanaged by the server.

Note that server 102 can, similarly, be any type of a processing devicefrom any manufacturer. Many types of processing devices can be used toimplement server 102. Additionally, different types of software fromthose specifically discussed herein can be run on server 102 to achievethe same functionality described in the present invention. Multiplecomputers or devices can be used to achieve the functionality of themanaging server, discussed herein. In the preferred embodiment, themanaging server executes software manufactured by Jareva Technologies,Inc., and referred to as “OpForce.” Other software that performsfunctionality described herein manufactured by Jareva Technologies,Inc., includes “ActiveOS” and “OpBoot.”

A preferred embodiment of the invention executes on Intel x86 chips andis written in a standard Linux INITRD format. OpBoot is treated as aNetwork Boot Program (NBP) within the Linux environment as defined bythe PXE (Pre-boot Execution Environment) standard. Steps accomplished bythis preferred embodiment are listed in Table I, below.

TABLE I 1. Initialize and read parameters form DHCP option-135 (see,e.g., DHCP standard RFC-2131 for description of DHCP options); 2. TFTPthe two ActiveOS files into extended memory into the standard locationsdefined by Linux; and 3. Jump to the start of the Linux kernel (asdefined by Linux).

Another embodiment executes on a Solaris platform. The Solaris versionof the ActiveOS is a miniaturized version of the Sun Solaris OS. Abootstrap program is TFTPed and the rest of the ActiveOS is NFS mountedusing the standard Solaris mechanisms. It should be apparent that anytype of software that achieves the functions, operations and otheraspects of the invention can be suitable for use in accordance with theinvention and is within the scope of the invention, as claimed.

A preferred embodiment of the invention uses popular standardizedprotocols to allow the managing server to prepare target machines forcommunication and operation upon boot-up. The Dynamic Host ConfigurationProtocol (DHCP) is used to automate the assignment of Internet Protocol(IP) addresses in the resource network. A Bootstrap Protocol (BOOTP)along with DHCP options and BOOTP vendor information extensions is alsoused. This allows target machines without disks and specificbootstrapping software to discover the target machine's own IP address,the address of a server host and the name of a file to be loaded intomemory and executed. Descriptions of these protocols can be found on theInternet, or by reference to the following Request For Comments (RFCs):RFC9510, RFC2131 and RFC2132. Other protocols for communicating withinthe DHCP framework include: Boot Control Transfer Protocol (BCTP),Trivial File Transfer Protocol (TFTP), user datagram protocol (UDP) andothers. It should be apparent that the specific use of these protocolsis not necessarily to practice the invention. In general, any type ofprotocol, communication scheme, network architecture, etc. can beacceptable for use with the present invention.

A preferred embodiment of the invention uses a mechanism whereby, uponpowerup, a target machine communicates to the server that the targetmachine is ready to boot. In the preferred embodiment, each targetmachine is provided with a Network Interface Card (NIC) such as one thatfollows the Preboot Execution Environment (PXE) standard. The PXE NICbroadcasts a “ready-to boot” message to the server upon powerup. Theserver then transfers an executable object to the target machine. In acontemplated embodiment, the executable object is about 8 MB and iscalled ActiveOS. ActiveOS is loaded and executed via instructions inOpBoot onto the target machine. ActiveOS then inspects the targetmachine to discover the hardware configuration, basic input/outputsystem (BIOS) version and other aspects of the target machine. In thepreferred embodiment, ActiveOS runs completely in memory so that no harddisk is needed since some target machines may not have a hard disk.ActiveOS is based on LINUX and launches a LINUX kernel to put up aTCP/IP stack.

Table II shows some of the information discovered and sent back to theserver by ActiveOS.

TABLE II Memory Hard disks Central Processing Unit (CPU) Motherboardchip set System management (BIOS) information Serial number Model nameBIOS date/version Computer manufacturer BIOS vendor Computer CPU familyBlade Chassis Location (if it is a blade) Blade chassis serial number(if it is a blade) Blade chassis IP address (if it is a blade) Bladechassis model (if it is a blade) Rack serial number Network cards

Table III shows an example of a format used to report information backto the server in a preferred embodiment. Note that other embodiments canuse any suitable format. The protocol used in Table III is BCTP.

TABLE III StatusComplete 1 memsize=128; arch=i686; chipset=8086.7124;cpus=1; cpumhz=598; net={count=2; 0={name=eth0; type=Ethernet;hwaddr=00:D0:B7:7E:94:BA}; 1={name=eth1; type=Ethernet; hwaddr00:90:27:F9:5B:B5}}; hd={count=1; 0={name=/dev/hda; size=13}};smbios={BSmanufacturer={Intel\sCorp.};BSversion={CA81020A.86A.0005.P02.99113004264; BSreleaseDate={Nov. 30,1999}; MBcpuCount=1; MBavgCpuMhz=600; MBcpuFamily=17; MBmem=128}

In the preferred embodiment, the information in Table II, and additionalinformation, as desired, is acquired from the target machine whenActiveOS receives a request from the server to generate hardwareinformation. The results of discovering hardware information are sentback to server 102 in the form of scoped attribute value pairs in BCTPprotocol. Again, other formats can be employed.

After discovery, the server provides a provisioning agent to the targetmachine. The provisioning agent is used to install desired software onthe target machine. Since different hardware configurations requiredifferent types, or versions, of software, the provisioning agent is notloaded until after the hardware configuration of the target machine hasbeen discovered. In a preferred embodiment, the provisioning agent ispart of the ActiveOS.

A management system on the server receives a request eitherautomatically, or from a user, that provides a definition of how toconfigure the target machines and other resources. The servercommunicates to the provisioning agent which software to install. Theprovisioning agent can also obtain the software to be installed from theserver or from a different source.

By default, the provisioning agent obtains the software from a storageserver, such as an NFS server, a CIFS server, the OpForce server, etc.In general, the software can be obtained from any server connected tothe network using a variety of protocols including custom software.OpForce supports a form of software called “ActiveOS software”. The usercan write a custom program that runs on the ActiveOS. This program isfree to implement a protocol and gather information from any serverreachable on the network. In fact, the user can use this to extend thehardware detection that we already do.

The user first writes a standard Linux based application. Thisapplication is the uploaded into the OpForce system and placed on astorage server. When requested by the user, OpForce tells the ActiveOSto execute the software stored on the storage server. The BCTP messageslooks similar to those shown in Table IV.

TABLE IV SetAppDir nfs nfsserver:/directory Modify myExecutable 1argument1

When receiving this message, the ActiveOS accesses the NFS server,obtains the executable, and executes it.

Table V, below, shows basic steps in a procedure for controlled bootingof a target machine where the target machine uses an Intel x86architecture. Table V also shows, in curly brackets, the alternativeprotocol to be used when the machine is a SOLARIS type of machine asmanufactured by SUN Microsystems, Inc., rather than an Intel machine. Ina similar manner, other types of machines can be accomodated.

TABLE V 1. Use DHCP {Solaris = RARP} broadcast to find MAC 2. OpForce(or other server software) allocates IP and send DHCP {Solaris = RARP}response 3. Target downloads OpBoot through TFTP {Solaris = not used} 4.OpBoot downloads ActiveOS through TFTP {Solaris = NFS}

Different versions of ActiveOS are downloaded depending on the detectedplatform (e.g., SOLARIS OR INTEL). A preferred embodiment automaticallydetermines the correct ActiveOS to use without any user input. DHCPoption 60 (see the PXE standard), includes a string containing thearchitecture that is used to automatically select the correct ActiveOS.The target machine is then booted into the ActiveOS as previouslydescribed. ActiveOS is then used to discover the hardware in themachine. These are all done automatically without any user input andwithout any OS on the machine's hard disk. Other embodiments can usedifferent degrees of manual and automatic operations.

FIG. 2 illustrates the steps of Table V. In FIG. 2, managing server 202controls the boot-up of target machine 204. For ease of illustration,only a single target machine, and single type (Intel architecture) oftarget machine, is discussed.

Upon power-up, target machine 204 sends a notification to managingserver 202. In the preferred embodiment, the notification is made usinga PXE card installed in the target machine. In other embodiments,different notification mechanisms can be used. PXE uses the DHCPprotocol to generate a request, or notification. OpForce, executing inthe managing server, receives the request, allocates an IP address andsends a response. Next, the target machine requests a download ofsoftware from the managing server. This results in the managing servertransferring OpBoot. The target machine then executes OpBoot whichrequests a download of ActiveOS. ActiveOS is provided by the managingserver and is installed and run on the target machine.

Automated Boot from Disk Image

After ActiveOS is loaded, one option provided by the system of thepresent invention is to allow the target machine to boot from a diskimage. This option is very useful for systems, such as personalcomputers, that are designed to boot from a floppy disk. Preferably, thedisk image is in random-access memory (RAM), but any type of storage,other than storage device that typically reads the disk image, ispossible. The disk image can be distributed automatically from themanaging server to one or more target machines. The procedure describedherein is designed for PC platforms but other types of platforms can behandled in a similar manner.

Table VI shows steps in a procedure to boot a target machine from a diskimage without requiring the placement, or existence, of a diskcontaining the image into a drive in the target machine.

TABLE VI 1. Load Managing Software onto target machine. 2. Setup DHCP toboot 1.44 MB image 3. Use BCTP to reboot target 4. Target sends DHCPrequest (step 1 of FIG. A) 5. OpForce server sends DHCP response 6.Target downloads OpBoot 7. OpBoot “boots” floppy image 8. Run userutility 9. Use OpBoot network stack to return result 10. OpForce serversets DHCP to load back to ActiveOS 11. Reboot target

After step 1 of Table VI, it is assumed that Managing Software has beenloaded into the target machine. Such software can be loaded, forexample, as described above with respect to the ActiveOS software. In apreferred embodiment, the ActiveOS software, OpBoot and OpForce softwareperforms the remaining steps of Table VI. Note that the operations, orsteps, of Table VI can be performed by one or more types of differentsoftware and can be performed at one or more points in a system, such asthe system of FIG. 1.

At step 2, DHCP is set to boot a standard 1.44 MB floppy image. The DHCPboot file is set to boot OpBoot (offset 0x6c in the DHCP packet). TheDHCP specification defines a number of DHCP options. Options areidentified by numeric numbers. DHCP option 135 passes an argument toOpBoot. This argument contains the name of the 1.44 MB image to download(via TFTP). An example of the argument format is: dhcp option-135“dos=floppyimage.bin;additional arguments”. The string “additionalarguments” is returned on a call to vector 0xA1 (see step 8).

At step 3, BCTP is used to reboot the target machine.

Steps 4, 5 and 6, are similar to steps 1, 2 and 3, respectively of TableV. At step 4, the target machine uses DHCP to broadcast a request to theserver to obtain an IP address. At step 5, the server sends a response.The target machine downloads boot software, such as OpBoot.

At step 7, the boot software obtains and boots to a floppy image. Thefloppy image can be the exact image that would reside on a floppy diskused to boot a PC from a disk drive. The floppy image is obtained fromthe server, or from some other source over, e.g., a network connection.It is not necessary for the target machine to obtain the floppy imagefrom the floppy drive or from some other media-reading device connectedto the target machine.

At step 8, the floppy image is executed to execute operations inaccordance with the floppy image. These operations can be “user”directed such as installing and executing specific versions of operatingsystems, applications, drivers, utilities, etc. In general, any type ofoperation that can be performed by a floppy image in the traditionalboot-up procedure (i.e., where the disk image is read from a floppydrive) can be performed using the system of the present invention.

The approach of the present invention may provide additional advantagesnot possible with the prior art approaches. For example, it may bepossible to have a boot image that is greater than the 1.44 MB capacityof the physical floppy medium. Also, the booting process is not slowedby reading of a floppy disk or other physical media. This may allowadvantages such as monitoring or diagnostics during the boot-up phase.

The arguments passed from the DHCP option-135 can be retrieved using theBIOS vector 0xA1. The OpBoot API provides functions that the user cancall to access PXE services from within a standard MS-DOS program. It isaccessed via INT A1h and is only accessible when booting MS-DOS bootimages. Table VII, below, shows some of these functions. Not all of thefunctions use PXE parameters.

TABLE VII Services: Get version In: AX=0000h Out: AL = version AH =error code CF set on error Get boot parameters In: AX=0001h Out: ES:DI =points to null terminated character string AH = error code CF set onerror Get boot server IP In: AX=0002h Out: EBX = boot server IP addressAH = error code CF set on error Get gateway IP In: AX=0003h Out: EBX =gateway IP address AH = error code CF set on error Get subnet mask In:AX=0004h Out: EBX = subnet mask AH = error code CF set on error Get IPaddress In: AX=0005h Out: EBX = IP address AH = error code CF set onerror Open network In: AX=0100h Out: AH = error code CF set on errorClose network In: AX=0101h Out: AH = error code CF set on error Readnetwork In: AX=0102h CX = size of buffer DX = destination port, ES:SI =buffer to read into Out: AH = error code CF set on error CX = number ofbytes actually read Write network In: AX=0103h EBX = IP address ofdestination CX = number of bytes to write EDX>>16 = destination port, DX= source port, ES:SI = buffer to write Out: AH = error code CF set onerror

At step 9, the OpBoot network stack is used to return results to theserver. This step is explained in more detail in co-pending the patentapplication referenced above, entitled “USE OF OFF-MOTHERBOARD RESOURCESIN A COMPUTER SYSTEM.”This step is useful where, for example, thepurpose of loading and executing the disk image is to run tests orgather other data from the system. In general, any type of informationcan be communicated.

At step 10, the target machine is set to load back to ActiveOS.

At step 11, the target machine is rebooted back to the Managing Softwarewhere the steps above can be repeated for another disk image, or fordifferent purposes, as desired. Note that it is not necessary to performall of the steps listed in Table VI to achieve advantages of the presentinvention. Also, additional steps may be included without detractingfrom the invention. The steps listed in Table VI are merely illustrativeof a preferred embodiment.

Next, details of step 7 of Table VI are discussed in connection withFIG. 3. It should be apparent that these details can be performed inaddition to other steps and need not have all operations executed inassociation with step 7 of Table VI.

FIG. 3 depicts a memory map of a PC to illustrate details of bootingusing a disk image. In FIG. 3, a BIOS native to the target machine isinstructed (e.g., through DHCP, etc.) to load OpBoot at an area of lowmemory. Although the invention is discussed with respect to specificboot software, such as OpBoot, any appropriate software or set ofinstructions can be used.

OpBoot communicates with the server via TFTP to load a disk image. Thedisk image is loaded to an unused portion of memory such as at 302. Inthe preferred embodiment, the disk image is an exact image as would bepresent on a bootable floppy disk. However, other embodiments can useimages that vary from such an image.

OpBoot changes vectors used by the native BIOS (e.g., the MSDOS BIOSmanufactured by Microsoft, Inc.) as shown in Table VIII.

TABLE VIII Vector Points to 0x11 Simulated Floppy Controller 0x13 mapsA: to disk image or B: to another disk image 0x15 Changed to reservedmemory for disk image or multiple disk images

In Table VIII, the BIOS vector 0x11 (also called “interrupt 11h” or “INT11h”) is the hardware list interrupt. It returns what hardware ispresent in the system. The preferred embodiment intercepts theinformation returned and changes the information about the floppy drivesin the system so that disk images are recognized as “physical” floppydrives.

Next, OpBoot is moved to a different memory location so it will notinterfere with the booting according to the disk image. Initially,OpBoot is placed in memory starting at location (hexadecimal) 7C00 byPXE. In a preferred embodiment, OpBoot is moved to below the 640K markat a later time, as shown at 304 of FIG. 3. In other embodiments, otherlocations can be used. Vector 0x15 is set to prevent other instructionsfrom accessing memory area 302.

OpBoot emulates BIOS operation by loading the first 512 bytes of floppydata (in this case the floppy image data) into memory at 7C00. The first512-bytes of the floppy then completes the “boot” of the floppy image.At this point, usually an OS, such as MS-DOS takes over. MS-DOS andMS-DOS programs use vector 0x13 to access the floppy drive. Usually 0x13calls are redirected into the BIOS. In this case, they get redirected toOpBoot.

The floppy drive is typically accessed as “A:” pointed to by vector0x13. Since vector 0x13 has been modified to point to the disk imagestored at 302, the BIOS, instead, obtains data from locations at 302. Atthis point programs running on top of the floppy OS (such as MS-DOS) canuse the vector 0xA1 (INT A1h) to obtain the arguments passed to it fromthe DHCP option-135.

As can be seen, the procedure described, above, essentially “tricks” theBIOS (or other operating system, kernel, boot-up routine, etc.) to usedata from memory instead of attempting to read boot-up data from afloppy (or other device or location). In the preferred embodiment, adynamic computing environment (DCE) is provided where many computers canbe connected together, on demand, and automatically configured withsoftware or made to perform desired tasks.

The ability to download bootable disk images to many target machines atboot-up (after power-up), allows a manager of the DCE to use customers'existing boot-up diskettes to create disk images that can be distributedinstantly, as desired. This is a huge benefit to the DCE manager and tocustomers, alike. The customers do not have to redefine, reformat orreprogram boot-up parameters and the DCE manager does not have toattempt to understand, analyze or explain how boot-up disk images mustbe changed or converted. Moreover, since the physical medium (i.e., thediskette) has been eliminated, the boot-up information can be easilystored, tracked and transferred.

Table IX, below, shows basic steps in the OpBoot operation.

TABLE IX Pseudo code for opboot: 1. Parse DHCP option 135 for argumentsand floppy image name(s). 2. Download each floppy image into extendedmemory (see INT 15h). 3. Relocate OpBoot from 7C00 to just below the640K mark. 4. Point the interrupt vectors 0x11, 0x13, 0x15, 0xA1 intoOpBoot's code. 5. Load first sector of floppy into memory 7C00 and jumpto it to complete boot process. 6. If a program (such as an MS-DOSprogram) calls vector 0x13, check if the program requested a floppydrive. If so, read and write the data from the downloaded image inextended memory instead of the physical floppy (if present). 7. If aprogram (such as an MS-DOS program) calls vector 0x11, fixup the floppydrive count to include the “fake” floppies in memory. 8. If a program(such as an MS-DOS program) calls vector 0x15, report the extendedmemory not including the memory reserved for the floppy images. 9. If aprogram (such as an MS-DOS program) calls vector 0xA1, return therequested information. If the request was for the para- meters passed inDHCP option-135, use a saved copy of the parameters.

Although the system of the present invention has been described withrespect to specific embodiments thereof, these embodiments areillustrative, and not restrictive, of the invention. For example,although the invention has been discussed primarily with respect tofloppy disk images, it is possible to emulate booting of CD-ROM, tape orother media in similar manner to that described herein. Multiple diskimages can be used. For example, B:, C:, D:, and other drives or devicescan be redirected so that the BIOS obtains information from such devicesfrom memory locations. Further, this approach eliminates the need forhaving extra peripherals, such as floppy drives, connected to everymachine.

Thus, the scope of the invention is to be determined solely by theappended claims.

1. A method comprising copying information stored in a physical mediumof a computer system to an electronic file; storing the electronic filein random access memory of the computer system; changing one or morecharacteristics in the computer system so that a process executing inthe computer system is provided with data from the stored electronicfile when an access to a physical device is attempted; using thecomputer system for executing at least a portion of the information inthe random access memory; modifying a vector in the computer system sothat an access to a disk drive results in an access to at least aportion of the information in the random access memory; and modifyingthe contents of a vector location to point to at least a portion of theinformation in the random access memory.
 2. The method of claim 1,wherein the vector location is vector location 0x13.
 3. The method ofclaim 2, wherein the vector location 0x13 contains the location of atleast a portion of the information in the random access memory.
 4. Themethod of claim 2, wherein the vector location 0x13 indirectly points tothe at least a portion of the information in the random access memoryvia one or more intermediary data structures or instructions.
 5. Themethod of claim 2, further comprising: modifying the contents of vectorlocation 0x11 to simulate one or more disk drives.
 6. An apparatuscomprising: a physical medium; a random access memory; a computersystem, comprising the physical medium and the random access memory; andinstructions stored within the computer system, the instructionsconfigured to cause said computer to copy information stored in thephysical medium to an electronic file, store the electronic file in therandom access memory, change one or more characteristics in the computersystem so that a process executing in the computer system is providedwith data from the stored electronic file when an access to a physicaldevice is attempted, use the computer system for executing at least aportion of the information in the random access memory, modify a vectorin the computer system so that an access to a disk drive results in anaccess to at least a portion of the information in the random accessmemory, and modify the contents of a vector location to point to atleast a portion of the information in the random access memory.
 7. Themethod of claim 6, wherein the vector location is vector location 0x13.8. The method of claim 7, wherein the vector location 0x13 contains thelocation of at least a portion of the information in the random accessmemory.
 9. The method of claim 7, wherein the vector location 0x13indirectly points to the at least a portion of the information in therandom access memory via one or more intermediary data structures orinstructions.
 10. The method of claim 7, further comprising: modifyingthe contents of vector location 0x11 to simulate one or more diskdrives.
 11. A computer program product comprising: a first set ofinstructions, executable on a computer system, configured to copyinformation stored in a physical medium of a computer system to anelectronic file; a second set of instructions, executable on a computersystem, configured to store the electronic file in random access memoryof the computer system; a third set of instructions, executable on acomputer system, configured to change one or more characteristics in thecomputer system so that a process executing in the computer system isprovided with data from the stored electronic file when an access to aphysical device is attempted; a fourth set of instructions, executableon a computer system, configured to use the computer system forexecuting at least a portion of the information in the random accessmemory; a fifth set of instructions, executable on a computer system,configured to modify a vector in the computer system so that an accessto a disk drive results in an access to at least a portion of theinformation in the random access memory; a sixth set of instructions,executable on a computer system, configured to modify the contents of avector location to point to at least a portion of the information in therandom access memory; and computer readable media, wherein said computerprogram product is encoded in said computer readable media.
 12. Thecomputer program product of claim 11, wherein the vector location isvector location 0x13.
 13. The computer program product of claim 12,wherein the vector location 0x13 contains the location of at least aportion of the information in the random access memory.
 14. The computerprogram product of claim 12, wherein the vector location 0x13 indirectlypoints to the at least a portion of the information in the random accessmemory via one or more intermediary data structures or instructions. 15.The computer program product of claim 12, further comprising a seventhset of instructions, executable on a computer system, configured tomodify the contents of vector location 0x11 to simulate one or more diskdrives.
 16. An apparatus comprising: means for copying informationstored in a physical medium of a computer system to an electronic file;means for storing the electronic file in random access memory of thecomputer system; means for changing one or more characteristics in thecomputer system so that a process executing in the computer system isprovided with data from the stored electronic file when an access to aphysical device is attempted; means for using the computer system forexecuting at least a portion of the information in the random accessmemory; means for modifying a vector in the computer system so that anaccess to a disk drive results in an access to at least a portion of theinformation in the random access memory; and means for modifying thecontents of a vector location to point to at least a portion of theinformation in the random access memory.